Oil compositions

ABSTRACT

Esters of substituted phosphinic or thiophosphinic acid and a phenolic compound in which a quaternary carbon substituent is ortho to the hydroxyl group improve the oxidation stability at elevated temperature of mineral and synthetic oils.

smite Sttes Patent [191 Gersmann et a1.

[ OIL COMPOSITIONS [75] Inventors: Hans R. Gersmann; Geert Van Bruggen, both of Amsterdam,

Netherlands [73] Assignee: Shell Oil Company, New York, NY. [22] Filed: May 30, 1972 [21] Appl. No.: 257,631

[30] Foreign Application Priority Data June 2, 1971 Great Britain 18591/71 [52] US. Cl 252/46.7, 252/467, 252/498, 252/499, 260/944, 260/961 [51] Int. Cl C10m 1/48 [58] Field of Search 252/466, 46.7, 49.8, 49.9

[56] References Cited UNITED STATES PATENTS 3,088,917 5/1963 Friedman et al 252/498 X 1 Dec. 10, 1974 Orloff et a1. 252/467 X 3,321,401 5/1967 Ford et a]. 252/467 3,493,638 2/1970 Meltsner 252/498 X 3,553,131 1/1971 Hepplewhite et al... 252/467 3,718,590 2/1973 Clark 252/467 3,748,269 7/1973 Clark 252/467 X Primary ExaminerH. Sneed Attorney, Agent, or FirmHenry C. Geller [5 7 ABSTRACT 5 Claims, No Drawings on. coMsrTroNs BACKGROUND OF THE INVENTION It is common practice to add certain compounds to mineral and synthetic oils to improve the oxidation stability. Most compounds that have so far been proposed for this purpose show a strongly decreasing antioxidant activity at increasing temperature, one of the reasons for this being oxidative decomposition. As long as the oils are employed at relatively low temperatures, this property of the anti-oxidants is not harmful. However, as soon as the oils are used under conditions in which they are exposed to relatively high temperatures, for example, as lubricating oils for combustion engines, this property of the anti-oxidants present in the oils constitutes a serious drawback. In this connection it should be observed that especially of recent years there has been a clear tendency to increasing thermal engine load, as a result of which, ever-increasing demands are put on the oxidation stability of lubricating oils for these engines.

E. N. Walsh in US. Pat. No. 2,860,155, issued Nov. 1 l, 1958, discloses certain phosphinate esters from which are made plasticizers and linear polyphosphonate resins.

SUMMARY OF THE INVENTION There has now been found a novel class of compounds which have proved to be advantageous for improving the oxidation stability at elevated temperature of mineral and synthetic oils. This class of novel compounds consists of esters which are represented by the general formula wherein X is oxygen or sulfur, R is a hydrocarbyl group, which may be substituted with one or more hetero atoms or hetero groups, and R is a naphthalene ring, which may be substituted, or a benzene ring which carries at one ortho position with respect to the oxygen atom a hydrocarbyl group which is attached to the benzene ring nucleus via a quaternary carbon atom, and which benzene ring may contain other substituents such as halogen atoms, hydroxyl groups, nitro groups and the like. The invention therefore relates to the aforementioned novel esters and to compositions comprising one or more mineral and/or synthetic oils or fuels and one or more of these esters.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The esters of the invention are esters of hydrocarbylphosphinic acids or hydrocarbylthiophosphinic acids,

mula may denote several types of hydrocarbyl groups such as an alkyl group, a cycloalkyl group, an aryl group, an alkaryl group, an arylalkyl group. Compounds wherein R stands for an aromatic group such as a phenyl group are very suitable. As described above, R may be substituted with one or more heteroatoms or hetero groups, for example, a halogen atom, a nitro group, a substituted or unsubstituted amino group, and the like. An advantageous substituent is a chlorine atom, such as a chlorine atom in a benzene ring, in particular in the para position with respect to the carbon atom of the benzene ring which is attached to the phosphorus atom. Preferably R' is a phenyl group or a phenyl group substituted with a chloro group, a C alkyl, or a lower alkyl amino group. Where the substituent is C alkyl, i.e., methyl through hexyl, representative R groups include tolyl, ethylphenyl, propylphenyl, isopropylhexyl, hexylphenyl and the like. Representative lower alkyl amino substituents include amino groups substituted with alkyls of l to 4 carbon atoms such as methylamino, dimethylamino, ethylamino, methylethylamino, and the like.

The esters of the invention are derived from a naphthol or preferably from an alkylphenol ROH, wherein R is a benzene ring which carries at one ortho position with respect to the hydroxyl group a hydrocarbyl group which is attached to the benzene nucleus via a quaternary carbon atom; this hydrocarbyl group very suitably contains not more than 20 carbon atoms, and is preferably an aliphatic group, in particular a tertbutyl group. If desired the benzene nucleus in the alkylphenol ROH may contain one or more other substituents, which may be hydrocarbyl groups or substituted hydrocarbyl groups and/or heteroatoms and/or hetero groups, for example, halogen atoms, hydroxyl groups, nitro groups, and the like. As examples of very suitable alkylphenols of which the esters of the invention may be derived are 2-methyl-6-tert-butylphenol, bis(3,5-di-tert-butyl-4- hydroxyphenyl)methane, and in particular 2,6- ditertbutyl-4-methylphenol or 2,4-dimethyl-6-tertbutylphenol, in the latter two cases R representing ...H3.c.. --Cl-h or CH3 respectively.

JXCI-Ia); XCHa)! Since the synthesis of esters of hydrocarbylphosphinic acids and phenols which are substituted at both ortho positions relative to the hydroxyl group with a hydrocarbyl group which is attached to the benzene nucleus via a quaternary carbon atom, is in many cases difficult owing to the bulky groups around the hydroxyl group, esters of hydrocarbylphosphinic acids and phenols which at only one ortho position are attached to a quaternary carbon atom, are preferred in case they are on the same performance level with respect to the desired properties. As examples of preferred esters which are advantageous for use in compositions of the invention are the esters of 2,4-dimethyl-6-tertbutylphenol and phenylphosphinic acid, p-chlorophenylphosphinic acid, phenylthiophosphinic acid or p-chlorophenylthiophosphinic acid.

A preferred group of the esters of the invention may be represented by the formula i u -on,

n 2: wherein X is oxygen or sulfur, R is Y is hydrogen, chloro, C alkyl or lower alkyl amino, and R is a phenyl group with at least one tert-butyl substituent ortho to the connecting oxygen atom and containing to 30 carbon atoms. A more preferred class of compounds is that in which Y is hydrogen or chloro. Especially preferred are compounds wherein Y is hydrogen or chloro and R has from 12 to 15 carbon atoms.

The esters of the invention can be prepared in any desired way. For example, they can be prepared by reacting a hydrocarbyl dichlorophosphine, or substituted hydrocarbyl dichlorophosphine, with an alphaor beta naphthol or with a phenol containing a hydrocarbyl group which is attached via a quaternary carbon atom to the benzene nucleus at an ortho position with respect to the hydroxyl group, in the presence of a tertiary ammonium compound, and subsequent partial hydrolysis of the reaction product obtained.

The esters may also be prepared by reacting a hydrocarbyl dichlorophosphine, or a substituted hydrocarbyl dichlorophosphine, with an alkali salt, e.g, sodium salt, of a naphthol or of a phenol containing a hydrocarbyl group which is attached via a quaternary carbon atom to the benzene nucleus at an ortho position with respect to the hydroxyl group, with liberation of an alkali chloride, and subsequent partial hydrolysis of the reaction product obtained.

It has been found that oil compositions, particularly lubricating oil compositions, containing the esters of the invention possess anti-wear properties under extreme pressure.

The esters according to the invention may be incorporated in oils or liquid hydrocarbon fuels More than one ester can be used. Examples of fuels include heavy residual fuels, distillate fuels such as gasoline, aviation turbine fuel, gas oil and the like. The esters can also be incorporated in oils, e.g., a crude mineral oil; prefera bly, they are incorporated in lubricating oils, which may be a mineral or synthetic oil or mixtures thereof. Examples thereof include lubricating oil for combustion engines and lubricating oils for steam turbines and further mineral and synthetic functional liquids such as hydraulic oils, heat transfer oils and automatic transmission oils. Also, the esters of the invention can be incorporated in lubricating greases based on mineral or synthetic oils. The esters are of special importance for improving the oxidation stability of mineral lubricating oils or mixtures thereof. If the oils in which the esters of the invention are incorporated are mineral oils, they can be obtained from naphthenic, paraffinic, asphaltic or mixed base crudes and/or mixtures thereof, for example, neutral oils having viscosities of from 100 to 6500 SSU at 100F. The mineral oils may be oils obtained by straight distillation or oils which after distillation have been subjected to one or more refining treatments, such as extractions, dewaxing or a hydrogen treatment. They may contain residual components.

Synthetic lubricants suitable for the invention are of various types, such as aliphatic esters, silicones, polyalkylene oxides, polyphenyl ethers, fluorinated hydrocarbons, polyolefins, and phosphate esters. Examples of silicones include methyl silicone, methylphenyl silicone, methylchlorophenyl silicone, etc. Examples of polyalkylene oxides are polyisopropylene oxide, polyisopropylene oxide diether, and polyisopropylene oxide diester. Fluorinated hydrocarbons include fluorinated oils and perfluorinated hydrocarbons. Preferred synthetic lubricant base stocks are esters of alcohols having 1 to 20, especially 4 to l2, carbon atoms and aliphatic carboxylic acids having from 3 to 20, especially 4 to l2, carbon atoms.

Particularly suitable esters oils are diisooctyl adipate, diisodecyl adipate and mixtures thereof. Other preferred esters for use as base stocks in the present invention are esters of monocarboxylic acids having 3 to 12 carbons and polyalcohols, such as pentaerythiitol, dipentaerythritol, and trimethylolpropane. Pentaerythrityl and dipentaerythrityl esters of mixtures of C, acids are particularly suitable base oils for the compositions of the invention. Preparation of these esters is described in Eichemeyer, US. Pat. No. 3,038,859, issued June 12, 1962, and Young, US. Pat. No. 3,121,109, issued Feb. ll, 1964.

The concentration of the esters in the oils may vary within wide limits, but is suitably from about 0.1 to about 10 percent by weight, and preferably from about 0.2 to about 5 percent by weight. The esters can be added as such to the oils or in the form of a concentrate which has been prepared, for example, by incorporation of the esters in a small quantity of oil.

In addition to the esters of the invention, the oils may contain other additives, such as anti-corrosion agents, additives to improve the viscosity and the viscositytemperature behavior detergents and other substances which are usually added to the aforementioned oils. If desired, in addition to the esters of the invention, the oils may incorporate other compounds with an antioxidant and/or anti-wear action,

EXAMPLE 1 Preparation of the ester of 2,4-dimethyl-6-tertbutylphenol and p-chlorophenylphosphinic acid A suspension of the sodium salt of 2,4-dimethyl-6- tort-butylphenol in toluene was gradually added in about 2 hours to a solution of an equimolar amount of p-chlorophenylphosphinic acid in toluene at about C The mixture obtained was refluxed for 1 hour. After cooling water was added with stirring, the aqueous layer was discarded and the organic layer washed with an aqueous sodium hydrogen carbonate solution. After drying the toluene was distilled off, and the resi due recrystallized from hexane; melting point I l8l 19C. The other esters tabulated in Table l were prepared in an analogous manner. Their melting points are recorded in Table 1.

EXAMPLE [I The antioxidant activity of several compounds of the invention was tested in solution in a light machine oil derived from a paraffmic Middle East crude, which was treated with hydrogen-(sulfur content below 5 ppm), and which had an average molecular weight of 385, with the aid of the "Shaken Circulatory Oxidation Test. This test was conducted as follows.

been set to the desired temperature and at the same time clamped in a shaking machine which made a rapid backward and forward movement. With the aid of a level controller and the buret, the pressure was made 5 equal to atmospheric. The oxygen in the system was circulated at a rate of about liters per hour' At regu- Sh k Circulatory Oxidation Test lar intervals a buret reading was taken after the pressure, which was reduced as a result of oxygen pick-up, A cylindrical tube (capacity 35 ml) provided with a had been made equal to atmospheric. The test was terdip pipe and a supply and discharge tube for oxygen 10 minated after about 400 minutes or at any earlier mowas charged with 12 g of the oil to be tested. The tube ment when 50 ml of oxygen had been consumed. was connected to a circulation system which incorpo- Table I shows the results. In experiments I and 2 rated a gas buret of 100 ml and a gas circulation pump. (given for co p n) t o yg consumption was The air in the system was replaced by oxygen. The tube very fast; the compounds according to the invention was then placed in a thermostated oil bath which had showed a good anti-oxidant activity.

hu a a a Melting C0nc., Consumppoint. percent tion of 0?. Time, Sludge, Exp. N0 Compound weightml. min. mg. 1 50 10 HO- -CH3 4 H X Liquid 1. 0 24 '420 45 C6H131LOCH3 -1 =-o OH:

s H X 0.5 102 40 (CHa)1N-1 O CH;

- X J. 10 H X 110-114 0. 5 50 405 CH3 In all formulas stands [or J.-CIIJ EXAMPLE Ill The antiwear properties under extreme pressure of compounds 3, 5, l and l l were investigated in a fourball tester with a modified ASTM 2596 method. The modification used was that the load was not increased stepwise but gradually at a rate of 0.65 kg/s. In Table II the last nonseizure load (mean of 3 determinations) is given for 0.5 percent by weight solutions of the compounds in a mineral white oil. For comparison a 0.5 percent by weight solution of Cereclor 42, a commercial extreme-pressure additive which is a chlorinated paraffin wax with a chlorine content of 41-44 percent by weight, was also investigated.

Table II shows that a much higher load is needed for the oils containing the compounds of the invention in order to cause seizure than for undoped oil or oil containing Cereclor 42.

We claim as our invention:

1. A lubricant composition consisting essentially of a major amount of a mineral lubricating oil and from about 0.1 to about 10 percent by weight of a compound having the formula wherein X is oxygen or sulfur, R is F. Y i

Y is hydrogen, chloro. C alkyl or lower alkyl amino, and R is a phenyl group with at least one tert-butyl substituent ortho to the connecting oxygen atom and containing 10 to 30 carbon atoms.

2. The composition of claim 1 wherein Y is hydrogen or chloro.

3. The composition of claim 2 wherein R has from 12 to 15 carbon atoms.

4. The composition of claim 3 wherein X is oxygen.

5. The composition of claim 3 wherein X is sulfur. 

1. A LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR AMOUNT T OF A MINERAL LUBRICATING OIL AND FROM ABOUT 0.1 TO ABOUT 10 PERCENT BY WEIGHT OF A COMPOUND HAVING THE FORMULA
 2. The composition of claim 1 wherein Y is hydrogen or chloro.
 3. The composition of claim 2 wherein R has from 12 to 15 carbon atoms.
 4. The composition of claim 3 wherein X is oxygen.
 5. The composition of claim 3 wherein X is sulfur. 